Being accompanied with developing blue light emitting diodes (LEDs), LEDs are lately used for light sources of displays or traffic signals and furthermore become to be used in place of incandescent lamps or fluorescent lamps. As it is preferable that LEDs can be operated simply with AC driving of 100 V or the like in case that LEDs are used in place of incandescent lamps or fluorescent lamps, as disclosed, for example, in Japanese Patent Application Laid-Open No. HEI10-083701 and as shown in FIG. 5, a structure in which LEDs connected in series and/or parallel are connected to an AC power source 71 is known well. Here, S represents a switch.
On the other hand, integrating these LEDs connected in series and/or parallel into a monolithic type has been performed, as shown, for example, in Japanese Patent Application Laid-Open No. 2000-101136. In a structure shown in FIG. 6, for example, a semiconductor lamination portion is formed by, laminating, on a sapphire substrate 60, an i-GaN layer 61, an n-GaN contact layer 62, an n-AlGaN clad layer 63, an active layer 64 formed with an InGaN multi quantum well, a p-AlGaN clad layer 65, and a p-GaN contact layer 66 are laminated in order. And, followed, etching a part of the semiconductor lamination portion so as to expose the n-GaN contact layer 62, forming a groove 70 by etching a border part of adjacent LEDs up to the i-GaN layer 61, forming an SiO2 film 67 in the groove 70, forming a transparent electrode 68 on the p-GaN contact layer 66, and forming a metal electrode 69 so as to connect the n-GaN contact layer 62 and the transparent electrode 68. And here it is also disclosed that the LEDs are connected to the AC power source 71 by connecting each of metal electrodes to a first power source wire and a second power source wire alternatively and are connected in parallel with reverse direction one by one.
As described above, a plenty of light emitting units are formed by separating grooves for separating each of light emitting units electrically after laminating semiconductor layers on the substrate in order to form a light emitting device with a plurality of LEDs connected in series and/or parallel in a monolithic type. And, as a wiring film is formed on the separating groove, when a width of the separating groove is wide, a problem of a break in wiring may arise. Therefore, the separating groove is formed very narrow with a width approximately 2 μm. On the other hand, a method of dry etching is necessary to be used for etching a nitride semiconductor layer, because it is very hard and stable. As a result, contaminations of etched semiconductor materials or the like generated in the etching process are easy to deposit and to be embedded in separating grooves previously being formed.
As a result, the short-circuit occasionally arises due to the contaminations embedded in the separating groove, even if light emitting units are separated by forming the separating groves. Under the above-described condition, in case of the short-circuit between two vertically adjacent light emitting units as shown in FIG. 5, as only one light emitting unit becomes out of operating, a trouble is rather small. However, as an arrangement of the light emitting units is in a turned back structure or in a ring-shaped structure formed in a rectangular-shaped chip, the light emitting device does not work as a light source in case that the short-circuit through the semiconductor layer or the like arises between two light emitting units in one end and in another end or in a middle part of a series and/or parallel circuit.
On the contrary, if a width of separating grooves is made wider intending to enhance reliability in an electrical separation, wiring films become easy to break because insulating films are depressed into separating grooves, as wiring films are formed on a surface side of the semiconductor lamination portion intervening insulating films, and reliability of wiring films is reduced.